Re: [PATCH] 2.5.14 IDE 56

[Alan Cox]

> You are right on the money!
> There is about 35-40% throughput killjoy "copy-from-kernel-to-userspace".
> It is easy to demo if you have a bus analizer and can do accounting on the
> data io less the command block overhead.
> 
> CR3's are your friend, not ...

You should be able to verify that by using large O_DIRECT I/O's. The
block layer itself may well be part of the overhead. With the scsi layer,
the block->scsi handling code is definitely a bottleneck to performance